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Title: The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical

Abstract

Cycloheptatrienyl (tropyl) radical, C 7H 7, was cleanly produced in the gas-phase, entrained in He or Ne carrier gas, and subjected to a set of flash-pyrolysis micro-reactors. In this study, the pyrolysis products resulting from C 7H 7 were detected and identified by vacuum ultraviolet photoionization mass spectrometry. Complementary product identification was provided by infrared absorption spectroscopy. Pyrolysis pressures in the micro-reactor were roughly 200 Torr and residence times were approximately 100 μs. Thermal cracking of tropyl radical begins at 1100 K and the products from pyrolysis of C 7H 7 are only acetylene and cyclopentadienyl radicals. Tropyl radicals do not isomerize to benzyl radicals at reactor temperatures up to 1600 K. Heating samples of either cycloheptatriene or norbornadiene never produced tropyl (C 7H 7) radicals but rather only benzyl (C 6H 5CH 2). The thermal decomposition of benzyl radicals has been reconsidered without participation of tropyl radicals. There are at least three distinct pathways for pyrolysis of benzyl radical: the Benson fragmentation, the methyl-phenyl radical, and the bridgehead norbornadienyl radical. These three pathways account for the majority of the products detected following pyrolysis of all of the isotopomers: C 6H 5CH 2, C 6H 5CD 2, C 6D 5CHmore » 2, and C 6H 5 13CH 2. Finally, analysis of the temperature dependence for the pyrolysis of the isotopic species (C 6H 5CD 2, C 6D 5CH 2, and C 6H 5 13CH 2) suggests the Benson fragmentation and the norbornadienyl pathways open at reactor temperatures of 1300 K while the methyl-phenyl radical channel becomes active at slightly higher temperatures (1500 K).« less

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [3];  [3];  [3];  [4];  [4];  [5]; ORCiD logo [2]
  1. Univ. of Colorado, Boulder, CO (United States). Department of Chemistry and Biochemistry; National Renewable Energy Lab. (NREL), Golden, CO (United States). National Bioenergy Center
  2. Univ. of Colorado, Boulder, CO (United States). Department of Chemistry and Biochemistry
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
  4. National Renewable Energy Lab. (NREL), Golden, CO (United States). National Bioenergy Center
  5. Univ. of Colorado, Boulder, CO (United States). Department of Mechanical Engineering, Center for Combustion and Environmental Research
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division; USDOE
OSTI Identifier:
1439202
Alternate Identifier(s):
OSTI ID: 1260286
Grant/Contract Number:
AC02-05CH11231; AC36-99GO10337
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 145; Journal Issue: 1; Related Information: © 2016 Author(s).; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Buckingham, Grant T., Porterfield, Jessica P., Kostko, Oleg, Troy, Tyler P., Ahmed, Musahid, Robichaud, David J., Nimlos, Mark R., Daily, John W., and Ellison, G. Barney. The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical. United States: N. p., 2016. Web. doi:10.1063/1.4954895.
Buckingham, Grant T., Porterfield, Jessica P., Kostko, Oleg, Troy, Tyler P., Ahmed, Musahid, Robichaud, David J., Nimlos, Mark R., Daily, John W., & Ellison, G. Barney. The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical. United States. doi:10.1063/1.4954895.
Buckingham, Grant T., Porterfield, Jessica P., Kostko, Oleg, Troy, Tyler P., Ahmed, Musahid, Robichaud, David J., Nimlos, Mark R., Daily, John W., and Ellison, G. Barney. Tue . "The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical". United States. doi:10.1063/1.4954895. https://www.osti.gov/servlets/purl/1439202.
@article{osti_1439202,
title = {The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical},
author = {Buckingham, Grant T. and Porterfield, Jessica P. and Kostko, Oleg and Troy, Tyler P. and Ahmed, Musahid and Robichaud, David J. and Nimlos, Mark R. and Daily, John W. and Ellison, G. Barney},
abstractNote = {Cycloheptatrienyl (tropyl) radical, C7H7, was cleanly produced in the gas-phase, entrained in He or Ne carrier gas, and subjected to a set of flash-pyrolysis micro-reactors. In this study, the pyrolysis products resulting from C7H7 were detected and identified by vacuum ultraviolet photoionization mass spectrometry. Complementary product identification was provided by infrared absorption spectroscopy. Pyrolysis pressures in the micro-reactor were roughly 200 Torr and residence times were approximately 100 μs. Thermal cracking of tropyl radical begins at 1100 K and the products from pyrolysis of C7H7 are only acetylene and cyclopentadienyl radicals. Tropyl radicals do not isomerize to benzyl radicals at reactor temperatures up to 1600 K. Heating samples of either cycloheptatriene or norbornadiene never produced tropyl (C7H7) radicals but rather only benzyl (C6H5CH2). The thermal decomposition of benzyl radicals has been reconsidered without participation of tropyl radicals. There are at least three distinct pathways for pyrolysis of benzyl radical: the Benson fragmentation, the methyl-phenyl radical, and the bridgehead norbornadienyl radical. These three pathways account for the majority of the products detected following pyrolysis of all of the isotopomers: C6H5CH2, C6H5CD2, C6D5CH2, and C6H513CH2. Finally, analysis of the temperature dependence for the pyrolysis of the isotopic species (C6H5CD2, C6D5CH2, and C6H513CH2) suggests the Benson fragmentation and the norbornadienyl pathways open at reactor temperatures of 1300 K while the methyl-phenyl radical channel becomes active at slightly higher temperatures (1500 K).},
doi = {10.1063/1.4954895},
journal = {Journal of Chemical Physics},
number = 1,
volume = 145,
place = {United States},
year = {Tue Jul 05 00:00:00 EDT 2016},
month = {Tue Jul 05 00:00:00 EDT 2016}
}

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